In electronic devices, printed circuit boards, or PCBs, are used to mechanically support electronic elements which have their connection leads soldered onto copper pads in surface install applications or through rilled holes in the board and copper pads for soldering the part leads in thru-hole applications. A board style may have all thru-hole parts on the top or component side, a mix of thru-hole and surface mount on the top side just, a mix of thru-hole and surface install elements on the top and surface area install parts on the bottom or circuit side, or surface mount elements on the top and bottom sides of the board.
The boards are likewise used to electrically link the needed leads for each component using conductive copper traces. The part pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are developed as single agreed copper pads and traces on one side of the board just, double sided with copper pads and traces on the top and bottom sides of the board, or multilayer styles with copper pads and traces on top and bottom of board with a variable variety of internal copper layers with traces and connections.
Single or double sided boards consist of a core dielectric material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is engraved away to form the actual copper pads and connection traces on the board surface areas as part of the board production procedure. A multilayer board consists of a variety of layers of dielectric material that has actually been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All of these layers are lined up and then bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced with today's innovations.
In a typical four layer board style, the internal layers are frequently utilized to supply power and ground connections, such as a +5 V airplane layer and a Ground plane layer as the two internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Really intricate board designs may have a large number of layers to make the different connections for various voltage levels, ground connections, or for connecting the many leads on ball grid range gadgets and other big incorporated circuit bundle formats.
There are normally 2 types of product utilized to build a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet type, typically about.002 inches thick. Core material is similar to a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, normally.030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board style, there are 2 techniques used to develop the preferred number of layers. The core stack-up technique, which is an older innovation, uses a center layer of pre-preg material with a layer of core product above and another layer of core material listed below. This mix of one pre-preg layer and 2 core layers would make a 4 layer board.
The film stack-up technique, a newer technology, would have core product as the center layer followed by layers of pre-preg and copper material developed above and listed below to form the last variety of layers needed by the board design, sort of like Dagwood developing a sandwich. This method allows the manufacturer flexibility in how the board layer thicknesses are integrated to satisfy the finished product thickness requirements by differing the number of sheets of pre-preg in each layer. Once the material layers are completed, the entire stack undergoes heat and pressure that triggers the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.
The process of making printed circuit boards follows the steps listed below for a lot of applications.
The procedure of determining products, procedures, and requirements to fulfill the customer's specs for the board style based upon the Gerber file info supplied with the purchase order.
The process of transferring the Gerber file data for a layer onto an etch withstand film that is put on the conductive copper layer.
The traditional procedure of exposing the copper and other locations unprotected by the etch withstand movie to a chemical that gets rid of the unprotected copper, leaving the safeguarded copper pads and traces in place; newer processes use plasma/laser etching rather of chemicals to remove the copper product, permitting finer line definitions.
The procedure of lining up the conductive copper and insulating dielectric layers and pushing them under heat to activate the adhesive in the dielectric layers to form a strong board material.
The process of drilling all the holes for plated through applications; a second drilling process is utilized for holes that are not to be plated through. Details on hole location and size is included in the drill drawing file.
The procedure of using copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are placed in an electrically charged bath of copper.
This is required when holes are to be drilled through a copper area however the hole is not to be plated through. Prevent this procedure if possible because it adds cost to the ended up board.
The procedure of applying a protective masking product, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder used; the solder mask secures versus environmental damage, supplies insulation, secures against solder shorts, and protects traces that run between pads.
The process of coating the pad areas with a thin layer of solder to prepare the board for the ultimate wave soldering or reflow soldering procedure that will occur at a later date after the components have actually been put.
The procedure of using the markings for component designations and element outlines to the board. May be applied to just the top or to both sides if components are mounted on both top and bottom sides.
The process of separating multiple boards from a panel of identical boards; this procedure also enables cutting notches or slots into the board if required.
A visual examination of the boards; likewise can be the process of examining wall quality for plated through holes in multi-layer boards ISO 9001 consultants by cross-sectioning or other approaches.
The procedure of checking for connection or shorted connections on the boards by methods using a voltage in between various points on the board and figuring out if an existing flow occurs. Depending upon the board complexity, this process might require a specially designed test fixture and test program to incorporate with the electrical test system used by the board producer.